Brushless motor having lubrication oil gaps and a core with radially projecting poles

ABSTRACT

A brushless motor includes a coil for energizing a motor to thereby rotate a rotor of the motor, a core having a plurality of projection poles around which the coil is wound, a terminal pin serving as a relay in feeding electric current to the coil, a lead wire extending from a terminal end of the coil, and a bracket for fixedly holding the core. The lead wire is electrically connected with the terminal pin directly or indirectly fixed to the core; and the terminal pin is extended to outside of the motor through a through-hole of the bracket so as to electrically connect with a motor driving circuit.

This application is a Division of application, Ser. No. 08/620,322,filed on Mar. 22, 1996 now abandoned, which is a Rule 60 Divisionalapplication of patent application Ser. No. 08/361,097 filed Dec. 21,1994 now U.S. Pat. No. 5,635,736.

BACKGROUND OF THE INVENTION

The present invention relates to the construction of a brushless motorfor use in a disc-driving apparatus or the like employed mainly in aninformation processing field.

In recent years, there have been increasing developments of disc-drivingapparatuses which are compact and of high density. FIGS. 13 and 14 showa representative example of a product in the field relating to thepresent invention. The product shown in FIGS. 13 and 14 is a 2.5-inchmagnetic disc-driving apparatus developed by PrairieTek Corp. of theU.S.A. The drawings of FIGS. 13 and 14 are copied from a catalog of theproduct. There are demands for the development of portable typeapparatuses having high quality, namely, apparatuses which are compact,resistant to shock, make little noise, vibrate little, and consume asmall amount of electricity. Needless to say, there are also demands forthe development of a high quality brushless motor (abbreviated as"motor" in descriptions made below) for rotating a disc. Manufacturersare conducting reach to comply with the above demands. Further, it isnecessary for manufacturers to improve productivity not only inproducing motors but also in assembling apparatuses.

A bearing is one of the elements which determines the performance of themotor. As in the apparatus shown in FIGS. 13 and 14, a ball bearing hasbeen conventionally used as the bearing. A dynamic pressure fluidbearing has drawn attention and has been adopted as a bearing whichcomplies with the demands at a high level. The dynamic pressure fluidbearing comprises a cylindrical shaft; a hollow cylindrical metal sleevefitted thereon with a gap provided therebetween; and a herringbonegroove provided on the shaft or the sleeve. Lubricating fluid (oil) isfilled in the gap. With the rotation of a rotor, pressure is generatedin the fluid, thus supporting the rotor. Theoretically, the dynamicpressure fluid bearing is superior as the bearing of the apparatusaccording to the present invention, because the mechanism thereof has asmall volume; makes little noise because the rotor is supported throughoil; is resistant to shock; is not subject to the shaft becomingsignificantly eccentric due to integration effect because the load isreceived by the entire periphery of the shaft. The dynamic pressurefluid bearing has, however, a disadvantage that the performance thereofdeteriorates when oil becomes scanty and that an apparatus is pollutedby oil which flows out therefrom. Thus, it is necessary to solve thisproblem.

In addition to solving the problem of the dynamic ressure fluid bearinghaving a smaller volume and making less noise than the ball bearing,improvements are desired for other constituent elements of the motor.More specifically, there are demands in particular for an improvement inthe winding density of a coil and a reduction in the vibration of abracket and the like.

There is also a demand for an improvement in the construction of aportion for electrically connecting a member of the motor of adisc-driving apparatus and a control circuit thereof with each other.Conventionally, a terminal wire (called a lead wire in the followingdescription) of a driving coil is manually connected with a printedwiring board by soldering. But recently, it has become very difficult toperform this operation due to the miniaturization of the motor, andhence the development of a novel connection method is desired.Conventionally, a flexible substrate and a connector are used to connectthe coil and the control circuit, which makes it difficult to automatethe connection between the connector and the control circuit. Theminiaturization of the motor and the apparatus causes another problem inthat the volume of the flexible substrate and that of the connector aregreat relative to the volume of the motor and that of the apparatus.

Further, a hole used to insert the flexible substrate into the motor andremove it therefrom is sealed with sealing agent consisting of adhesiveagent to prevent air from permeating thereinto. Thus, skilled work andmuch time are required to seal the hole.

In addition, it is important to prevent the quality of the motor frombeing deteriorated in the process of assembling the motor. The motorconstituting the disc-driving apparatus is composed of precision parts,for example, the bracket, but the precision of the parts may be degradedwhen handled in the assembling operation. The bracket constitutes thebase of the motor, thus frequently contacting a motor-placing platform.Therefore, there is a possibility that the finished surface of thebracket will be damaged or soiled. Thus, before a product is shipped,whether or not the finished surface of the bracket has been damaged orsoiled is checked with a microscope. In this situation, the developmentof damage-preventing countermeasures is desired.

SUMMARY OF THE INVENTION

The present invention is intended to solve the above-described problemsof the conventional motor, namely, the problem of performancedeterioration of the dynamic pressure fluid bearing caused by outwardflow of oil from the dynamic pressure fluid bearing; low winding densityof a coil; high noise levels generated by vibration; inefficient of theoperation for connecting a circuit for driving a motor and the coilinstalled inside the motor with each other; inefficient air-sealingoperation; and a large volume of an electrical connection construction.

It is therefore an object of the present invention to provide animproved brushless motor and a disc-driving apparatus which is compact,has a high output and performance, and is manufactured with a highproductivity.

In accomplishing these and other objects, according to a first aspect ofthe present invention, there is provided a brushless motor comprising: acoil for energizing a motor to thereby rotate a rotor of the motor; acore having a plurality of projection poles around which the coil iswound; a terminal pin serving as a relay in feeding electric current tothe coil; a lead wire extending from a terminal end of the coil; and abracket for fixedly holding the core, wherein the lead wire iselectrically connected with the terminal pin directly or indirectlyfixed to the core; and the terminal pin is extended to outside of themotor through a through-hole of the bracket so as to electricallyconnect a motor driving circuit with each other.

According to a second aspect of the present invention, there is provideda brushless motor comprising: a coil for energizing a motor to therebyrotate a rotor of the motor; a core having a plurality of projectionpoles around which the coil is wound; a terminal pin serving as a relayin feeding electric current to the coil; two or more insulators forinsulating the core and other members from the coil; and an engagingportion, formed on the terminal pin, having a configuration differentfrom the configurations of other portions of the engaging portion, theengaging portion being disposed between end faces of portions, of thetwo insulators, opposed to each other to limit movement of the terminalpin in an axial direction thereof.

According to a third aspect of the present invention, there is provideda brushless motor comprising: a coil for energizing a motor to therebyrotate a rotor of the motor; a core having a plurality of projectionpoles around which the coil is wound; and a terminal pin serving as arelay in feeding electric current to the coil, a part of the terminalpin being rectangular in section.

According to a fourth aspect of the present invention, there is provideda brushless motor comprising: coil for energizing a motor to therebyrotate a rotor of the motor; a core having a plurality of projectionsaround which the coil is wound; a terminal pin serving as a relay infeeding electric current to the coil; a terminal holder for fixedlyholding the terminal pin on the core; and an engaging projection, formedon the terminal pin, having a configuration different fromconfigurations of other portions in a vicinity of the engaging portion,wherein the engaging projection of the terminal pin is brought intocontact with an outer end face, of the terminal holder, opposed to anouter periphery of the motor so as to limit a movement of the terminalpin in an axial direction thereof.

According to a fifth aspect of the present invention, there is provideda brushless motor comprising: a coil for energizing a motor to therebyrotate a rotor of the motor; a core having a plurality of projectionpoles around which the coil is wound; a terminal pin serving as a relayin feeding electric current to the coil; a terminal holder for fixedlyholding the terminal pin on the core; and an engaging portion, formed onthe terminal pin, having a configuration different from configurationsof other portions in a vicinity of the engaging portion, wherein theengaging portion of the terminal pin is pressed into the terminal holderso as to limit movement of the terminal pin in an axial directionthereof.

According to a sixth aspect of the present invention, there is provideda brushless motor comprising: a coil for energizing a motor to therebyrotate a rotor of the motor; and a core having a plurality of projectionpoles around which the coil is wound, a width of the core projectionpole on an inner peripheral side thereof being smaller than a width onthe outer peripheral side thereof by 0.1 mm or more.

According to a seventh aspect of the present invention, there isprovided a brushless motor comprising: a coil for energizing a motor tothereby rotate a rotor of the motor; and a core having a plurality ofprojection poles around which the coil is wound, wherein the coil beingwound from an outer peripheral side of the core projection pole towardan inner peripheral side thereof is jumped to the outer peripheral sidethereof halfway and wound toward the inner peripheral side thereof.

According to an eighth aspect of the present invention, there isprovided a brushless motor comprising: a coil for energizing a motor tothereby rotate a rotor of the motor; a core having a plurality ofprojection poles around which the coil is wound; and a bracket forfixedly holding the core, wherein a thickness of an inner peripheralside of a bottom wall of the bracket is greater than a thickness of anouter peripheral side of the bottom wall thereof by 0.2 mm or more.

According to a ninth aspect of the present invention, there is provideda brushless motor comprising: a bracket for fixedly holding a shaft; anda rotary sleeve tapered and surrounding the shaft with a certain gapprovided between the shaft and the sleeve, wherein the gap is so formedthat a distance between an end face of the sleeve and a member opposedthereto on an inner peripheral side of the sleeve is smaller than adistance on an outer peripheral side of the sleeve by 0.03 mm or more.

According to a tenth aspect of the present invention, there is provideda brushless motor comprising: a bracket for fixedly holding a shaft; arotary sleeve tapered and surrounding the shaft with a certain gapprovided between the shaft and the sleeve; and a stationary memberspaced at a certain interval from the sleeve and surrounding an outerperiphery thereof, wherein the gap is substantially cylindrical betweenan outer peripheral surface of the sleeve and an inner peripheralsurface of the stationary member and is so formed that a distance on anend face of the sleeve is smaller than a distance on an upper end sidethereof by 0.05 mm or more.

According to an eleventh aspect of the present invention, there isprovided a brushless motor comprising: a bracket for fixedly holding ashaft; and a conical rotary sleeve surrounding the shaft with a certaingap provided between the shaft and the sleeve, wherein an outer diameterof the sleeve on a lower end thereof is greater than a diameter of anupper end thereof by 0.1 mm or more.

According to a twelfth aspect of the present invention, there isprovided a brushless motor comprising a bracket for fixedly holding acore, wherein a cylindrical peripheral portion of the bracket is steppedin a vicinity of a bottom of the bracket such that a diameter of thestepped portion is smaller than those of other outer peripheral portionsby 0.8 mm or more.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clear from the following description taken in conjunction withthe preferred embodiments thereof with reference to the accompanyingdrawings, in which:

FIG. 1 is a sectional view showing a motor according to a firstembodiment of the present invention and a control board;

FIG. 2 is a plan view showing a coil-installed assembly of the motor inFIG. 1;

FIG. 3 is a sectional view showing the coilinstalled assembly of themotor in FIG. 1;

FIG. 4 is a plan view showing a terminal pin of the motor;

FIG. 5 is a side view showing the terminal pin of the motor;

FIG. 6 is a side view showing the terminal pin rotated by 90° from thestate shown in FIG. 5;

FIG. 7 is a sectional view showing a coil-installed assembly of a motorhaving an alternative arrangement of the terminal pin and terminal pinmounting structure, having an alternative arrangement of the terminalpin and terminal pin mounting structure, according to the presentinvention;

FIG. 8 is a sectional view showing a coil-installed assembly having afurther alternative arrangement of the terminal pin and terminal pinmounting structure, having a further alternative arrangement of theterminal pin and terminal pin mounting structure, according to thepresent invention;

FIG. 9 is a partial plan view showing details of a coil-installedassembly and a bracket, according to the present invention;

FIG. 10 is a partial sectional view of the coil-installed assembly andthe bracket shown in FIG. 9;

FIG. 11 is a sectional view showing details of a sleeve and a bracketand members disposed in the vicinity thereof, according to the presentinvention;

FIG. 12 is a partially enlarged view of the sleeve and members in thevicinity thereof shown in FIG. 11;

FIG. 13 is a plan view showing a conventional magnetic disc-drivingapparatus; and

FIG. 14 is a side view showing the conventional magnetic disc-drivingapparatus in FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the description of the present invention proceeds, it is to benoted that like parts are designated by like reference numeralsthroughout the accompanying drawings.

Aspects of the present invention provide various means to solve theabove-described problems. The summary of the present invention isdescribed below by itemizing the means so that the content thereof canbe easily understood. That is, items (A) through (J) indicateindependent aspects, respectively, of the invention, and an aspectdescribed in an item indicated by a letter together with a numericaldesignation (e.g. A1) belongs to the aspect indicated by the letter.

In the description to be made below, a board of a motor control circuitis called a control board; a wire-shaped conductive member used as arelay to feed electric current from a coil installed inside a motor tothe control board and vice versa is called a terminal pin; an insulationmember for holding the terminal pin is called a terminal holder; a wireextended from the coil and connected with the terminal pin is called alead wire; a plurality of coil-wound projections extending radially fromthe inner peripheral surface of a core and functioning as a magneticpath of a field magnet are called core projection poles; a member forinsulating the core and other members from the coil to which electriccurrent is fed is called an insulator; a member which constitutes thebase of the motor and through which the motor is connected with anapparatus is called a bracket; and a cylindrical member surrounding theouter peripheral surface of a shaft with a gap provided therebetween andconstituting a bearing is called a sleeve.

Construction for directly connecting motor and control circuit with eachother by means of terminal pin!

(A): A construction in which the lead wire is connectedly wound aroundthe terminal pin fixed to the core; and the terminal pin is axiallyextended to the outside of the motor to connect the terminal pin with amotor driving circuit electrically (FIG. 1).

(A1): A construction in which the terminal pin is mounted on an innerperipheral surface, of the core, disposed between the core projectionpoles; the lead wire is connectedly wound on one end of the terminalpin; and the other end of the terminal pin is extended to the outside ofthe motor (FIGS. 2, 3).

(A2): A construction in which the terminal holder is inserted into ahole of the bracket to insulate the bracket from the terminal pin andplace the terminal pin in position (FIG. 1).

(A3): A construction in which the terminal holder is pressed into thehole of the bracket or attached in close contact therewith so as to keepthe hole airtight (FIG. 1).

Construction of fixing terminal pin!

(B): A construction in which an engaging projection of the terminal pinis disposed between the end faces of portions, of two insulators,opposed to each other so as to limit the movement of the terminal pin inthe axial direction thereof (FIGS. 2, 3).

(C): A construction in which a part of the terminal pin circular orsquare in section is shaped into a rectangular configuration in section(FIGS. 4-6).

(D): A construction in which the engaging projection of the terminal pinis brought into contact with the outer end face of the terminal holder,namely, the side opposed to the outer periphery of the motor (FIG. 7) soas to limit the movement of the terminal pin in the axial directionthereof.

(E): A construction in which the projection of the terminal pin ispressed into the terminal holder so as to limit the movement of theterminal pin in the axial direction thereof (FIG. 8).

Construction of improving space factor of coil!

(F): A construction in which the width of the core projection pole onthe inner peripheral side thereof is gradually smaller than the width ofthe core projection pole on the outer peripheral side thereof in theradial direction thereof (FIGS. 9, 10).

(G): A winding method of jumping the coil being wound from the outerperipheral side of the core projection pole toward the inner peripheralside thereof to the peripheral side thereof, halfway, i.e., in themiddle thereof, to the outermost peripheral side thereof, and then,winding the coil toward the inner peripheral side thereof (FIGS. 9, 10).

Construction for improving rigidity for motor!

(H): A construction in which the thickness of the bottom of the bracketbecomes greater gradually from the outer peripheral side thereof towardthe inner peripheral side thereof.

Construction of preventing outflow of oil from bearing!

(J): A construction in which a gap between an end face of the sleeve anda member opposed thereto is set to be gradually smaller from the outerperipheral side of the sleeve toward the inner peripheral side thereofin the radial direction thereof (FIGS. 11, 12).

(K): A construction in which a gap between the outer peripheral surfaceof the sleeve and a member opposed thereto is set to be graduallysmaller toward the side of an opening of the sleeve, i.e., from theupper end of the sleeve toward the lower end thereof in the axialdirection thereof (FIGS. 11, 12).

(L): A construction in which the outer diameter of the sleeve is set tobe gradually smaller from the lower end thereof toward the upper endthereof (FIGS. 11, 12).

Construction for preventing finished surface for bracket from beingdamaged!

(M): A construction in which the bracket is stepped on a cylindricalperipheral portion thereof at the outer periphery of the bottom thereof(FIGS. 11, 12).

Because various means for solving the above described problems have beendescribed, the operation of each means will be described below.

In the aspect of the invention described in the item (A), the terminalpin connected with the lead wire is extended to the outside of the motorto directly connect the terminal pin with a control circuit disposedoutside. The terminal pin is mounted on the core. Then, the coil iswound around the core and at the same time, the lead wire is woundaround the terminal pin to connect the lead wire with the terminal pinelectrically by means of soldering or the like. Then, the terminal pinis inserted through the hole formed in the bracket so as to projectoutwardly terminal pin from the motor. The terminal pin is inserted intoa socket contact mounted on the control board to complete the electricalconnection. This construction has two operations of winding the coilaround the core and connectedly winding the lead wire around theterminal pin by means of an automatic machine, and directly connectingthe with the control board. That is, the aspect of the inventiondescribed in the item (A) provides a compact and simple construction forconnecting the terminal pin and the control circuit with each other.

As a preferable construction, the terminal pin is disposed in the innerperipheral surface, of the core, between the core projection poles. Theis wound about and connected lead wire with one end of the terminal pin,and the other end of the terminal pin projects outwardly from the motor.This construction has advantages in that the terminal pin-mounting spacecan be easily constructed; the operation of connecting the lead wire andthe terminal pin with each other can be easily performed by means of anautomatic machine; and the position of the socket contact mounted on thecontrol board allows parts to be mounted at high density. Needless tosay, the terminal pin may be disposed in the outer peripheral side ofthe core depending on the required arrangement of parts of the controlboard.

In installing the terminal pin on the core, it is preferable to form theterminal holder on a portion of the insulator. The insulator is made ofan insulating substance such as resin. The insulator has the function ofguiding the coil; insulating the core from the terminal pin; insulatingother members from the coil; and preventing the movement and removal ofthe terminal pin. Further, the construction described in the item (A)allows for the following construction: The construction (A2) in whichthe terminal holder is extended to be inserted into the hole of thebracket, and the construction (A3) in which the terminal holder ispressed into the hole of the bracket or attached to the hole in closecontact therewith. The construction (A2) provides the advantage ofinsulating the bracket from the terminal pin, and placing the terminalpin in position on the control board. The construction (A3) provides theadvantage of sealing the hole, thus maintaining airtightness and inaddition preventing dust from penetrating into the motor or theapparatus.

The aspect of the invention described in the item (B) concerns theconstruction for preventing the movement of the terminal pin by means oftwo insulators made of resin. In order for the terminal pin to functionas the connector, it is necessary to fix the terminal pin so as toprevent it from being moved or removed easily by an external force orthe like. Therefore, a through-hole is formed through the insulator inthe axial direction thereof so that the through-hole serves as theterminal holder into which the terminal pin is inserted. The engagingportion is formed at a portion of the terminal pin. The engagingprojection of the terminal pin is disposed between the end faces ofportions, of two insulators, opposed to each other. This constructioncauses the engaging portion to contact the end face of each hole formedon the insulator, thus preventing it from being moved in any directions.

The aspect of the invention described in the item (C) concerns theconfiguration of the terminal pin. When the terminal pin is used as theconnector, generally, the desired sectional configuration of thematerial of the terminal pin is a circular or square configuration inconsideration of its wide application. A part of the terminal pin, orpreferably the side of the terminal pin on which the lead wire is wound,is shaped into a rectangular configuration, and the hole of theinsulator is formed in conformity to the rectangular configuration ofthe terminal pin so as to use the hole as the guide of the terminal pin.This construction prevents the terminal pin from being rotated bytensile force generated when an end of the lead wire wound around theterminal pin is pulled. In addition, the lead wire-wound portion of theterminal pin can be bent in a desired direction. Further, the end faceof the terminal pin and those of the two insulators are brought intoclose contact with each other by sandwiching a shape-change point of theterminal pin at which the configuration of the sectional configurationthereof is changed between the opposed portions of the two insulators.This construction prevents the terminal pin from being moved in anydirection.

The aspect of the invention described in the item (D) concerns theconstruction for limiting the movement of the terminal pin to only onedirection. When the terminal pin is used as the connector, the forceacting on the terminal pin is great when the terminal pin is insertedinto the connector. Thus, the engaging projection is formed on theterminal pin to bring the terminal pin into the outer end face of theterminal holder, namely, the side opposed to the outer periphery of themotor. Frictional force between the terminal pin and the terminal holderis utilized or one end of the terminal pin is bent to limit the movementthereof in the opposite direction.

Similarly to the aspect of the invention of the item (D), the aspect ofthe invention described in the item (E) also concerns the constructionfor limiting the movement of the terminal pin in the axial directionthereof. The sectional configuration of the projection may be shapedinto a configuration different from that of the other portions of theterminal pin by clinching material of the pin laterally or may be shapedinto a circular configuration in section to expand the terminal holderuniformly in the circumferential direction thereof. This constructionhas a more airtight operation than that described in the item (A).

The aspect of the invention described in the item (F) concerns theconfiguration of the core in a plan view to improve the characteristicof the motor. Supposing that electric current for driving the motor isconstant, power consumption spent to drive the motor and heat generationcaused by the use of the electric current are proportional to theresistance value of the coil. Thus, it is necessary to design the motorso that the resistance value of the coil is minimized. In order toproduce the core having a configuration to improve the characteristic ofthe motor, the coil can be wound around it in order, and a winding spacecan be secured to adopt a thickest possible wire material. To this end,the width of the core projection pole on the outer peripheral sidethereof is set to be larger than the width on the inner peripheral sidethereof in the radial direction thereof.

The coil is wound around core in the order from the inner peripheralside thereof. When the width of the core on the outer peripheral side isgradually increased, a component force directed toward the innerperiphery of the core is generated in the first layer of the coilwinding from the inner to the outer peripheral sides, due to the tensileforce thereof and the tapered configuration of the core. Consequently,gaps are not generated between adjacent coils, and thus, when the firstlayer is wound around the core favorably, it is easy to overlay thesuccessive layers one on the other in order.

It is preferable to make the width of the core projection pole small tosecure the coil-winding space. The space for forming PAC (connectinglayered cores with each other by forming projections on the cores in thethickness direction thereof) for layering the cores is required. In asmall core, portions in the outer periphery of core projection poles areselected as the space for layering the cores. Therefore, the widths ofthe core projection poles cannot be reduced to less than the minimumvalue in manufacturing. In order to solve this problem, the width of thecore projection poles on the inner peripheral side thereof is reduced ina range not exceeding the magnetic saturation limit, while each of thecore projection poles on the outer peripheral side thereof have a widthnecessary for manufacture. In this manner, the core-winding space issecured.

Similarly to the aspect of the invention of the item (F), the aspect ofthe invention described in item (G) also concerns the construction forreducing the resistance value of the coil. That is, the aspect of theinvention of the item (G) aims at improving the space factor of the coilby winding the coil in efficient arrangement and efficiently utilizingthe spaces between core projection poles. When the coil is wound in apredetermined order from the inner peripheral side of the coreprojection pole, odd numbered layers are wound toward the outerperipheral side of the core while numbered layers are wound toward theinner peripheral side thereof. If the specified number of layers is odd,normally, the coil terminates when it has been wound from the innerperipheral side of the core toward the outer peripheral side thereof. Inthis case, the coil on the inner peripheral side of the core is thickwhile the coil on the outer peripheral side thereof is thin, and thetermination of the coil is at a position apart from the inner peripheralside of the core projection pole. That is, the fan-shaped space betweenthe adjacent core projection poles is not efficiently utilized by thisway of winding the coil. In order to solve this problem, the coil beingwound from the outer peripheral side of the core projection pole towardthe inner peripheral side thereof is, at a midway point between theouter and inner peripheral rides, jumped to the outermost peripheralside thereof and then wound toward the inner peripheral side thereof. Inthis way of winding, a large amount of coil is wound on the outerperipheral side of the core projection pole and the termination of thecoil is disposed at the innermost periphery of the core projection pole.Even though this action may be performed several times, it does notcause the coil to be wound on the core projection pole in disorder. Ifthe resistance value of the coil is the same as the conventional one,the number of winding times can be increased by an improved space factorof the coil and an output torque can be increased accordingly.

The aspect of the invention described in the item (H) concerns theconstruction for increasing the rigidity of the bracket. The motor foruse in the apparatus according to the aspect of the present invention isrequired to rotate accurately to obtain a very high recording densityand thus it is necessary that the motor has a low degree of vibrationand a high degree of rigidity. The increase in the thickness of thebottom wall of the bracket and in particular, the increase in thethickness of the inner peripheral side thereof is effective forobtaining a high degree of rigidity and a low degree of vibration andnoise. But the increase of the inner peripheral side of the bracket iscontradictory to the increase in the volume of the coil of the motor.Thus, it is difficult to increase the thickness of the bottom wall ofthe bracket and the inner peripheral side thereof. The diameter andthickness of the coil are small on the inner peripheral side of the coreprojection pole by winding the coil in such a manner that the diameterthereof is large on the outer peripheral side of the core projectionpole as described in the item (G). As a result, a space is provided onthe bracket side, which is preferable for applying the presentinvention.

The aspects of the inventions described in the items (J) and (K)concerns the construction for preventing the leakage of lubricating oilfilled on the dynamic pressure fluid bearing. The dynamic pressure fluidbearing of a shaft-fixing type comprises a bracket for supporting theshaft. A portion of the upper end face of the bracket is opposed to theend face of the sleeve on the opening side thereof, e.g. the lower endface of the sleeve, with a certain gap provided therebetween. Further, avertical cylindrical portion, of the bracket, adjacent to the lower endface thereof is disposed alongside the vertical peripheral portion ofthe sleeve, with a certain gap provided therebetween. The spacesurrounded with the outer peripheral surface of the sleeve and the upperend face of the bracket has a function of reserving oil which has leakedfrom the bearing, preventing it from flowing out from the motor, andsupplying oil to the gap between the shaft and the sleeve when oilbecomes scanty. The constructions described in the items (J) and (K)enable these functions to operate efficiently.

The above-described gap between the lower end face of the sleeve and thesurface, of the bracket, opposed thereto is approximately disc-shaped.The thickness of the disc is set to be smaller gradually from the outerperipheral side of the sleeve toward the inner peripheral side thereof.The gap causes the oil filled therein to be collected to the innerperipheral side of the sleeve due to a capillary phenomenon. This actionallows oil to be attracted toward the bearing, thus supplying oilcontinuously and preventing leakage of oil.

The gap continuous with the disc-shaped gap, namely, the gap between theouter peripheral surface of the sleeve and a member or a verticalcylindrical portion of the bracket is set to be gradually smaller fromthe upper end of the sleeve toward the lower end face of the sleeve. Asin the case of the gap between the lower end face of the sleeve and thesurface, of the bracket, opposed thereto, a similar action works,thereby allowing oil to flow toward the lower end face of the sleeve.

The construction described in the item (L) is similar to that describedin the item (K), but has an operation different from that of theconstruction described in the item (K). That is, with the rotation ofthe sleeve, centrifugal force acts on oil which has attached to theouter peripheral surface of the sleeve in the dynamic pressure fluidbearing of the shaft-fixing type. If the outer peripheral surface of thesleeve is conical, oil which has attached to the outer peripheralsurface of the sleeve is moved toward a large-diameter portion of theouter peripheral surface of the sleeve due to the resultant force ofcentrifugal force and adhesion force. In consideration of thisprinciple, the outer diameter of the sleeve at the lower end thereof isset to be larger than that of the other (upper) side thereof so as tomove the oil which has attached to the outer peripheral surface thereoftoward the lower end thereof. In other words, this construction has afunction of moving the oil toward the center of the motor. Then, the oilmoves toward the bearing due to the operation described in the item (G).

The aspect of the invention described in item (M) concerns theconstruction for preventing a machined surface of the bracket from beingdamaged. Normally, on the outer periphery of the bracket, there areformed a cylindrical guide for placing the motor in position and aring-shaped flange, disposed adjacently to the cylindrical guide, formounting the motor on the apparatus. The outer peripheral surface of thecylindrical guide and the lower surface of the ring-shaped flange haveaccurately finished surfaces, respectively. The cylindrical portionhaving an outer diameter approximately 1 mm smaller than that of thecylindrical guide is formed below the cylindrical guide so as to preventthe surface of the cylindrical guide and that of the ring-shaped flangefrom being damaged during assembly. While the motor is being moved ortransported, the motor is supported by the cylindrical portion. Thus,the finished surface is not brought into contact with motor-placingplatform, and hence, the finished surface can be prevented from beingdamaged.

The numerical values described display the apparent operations and areselected in a range which can be distinguished from errors inmanufacture.

As described above, the method, according to the aspect of the presentinvention, of electrically connecting the motor and the control circuitwith each other provides a simple connection construction for feedingelectric current, a simple insulation construction, and a simple sealingconstruction, unlike the conventional method of electrically connectingthe motor and the printed wiring board with each other. Further, thereasonable construction for fixing the terminal pin provides a stableconnector function; the improved configuration of the core allows thecoil to be wound around the core and layered one on the other in animproved manner and increases the space for accommodating the woundcoil; the space factor of the coil can be improved by the reasonablewinding pattern which effectively utilizes the space in the outerperiphery of the core; and the rigidity of the motor can be increased bythe favorable thickness distribution of the bracket which utilizes theadvantage of the winding pattern. In addition, the mechanismsconstructed in the outer periphery of the sleeve utilize the propertiesof oil to prevent the oil from flowing out from the bearing. Moreover,the stepped portion formed on the cylindrical portion of the bracket canprevent the bracket from being damaged.

Next, the above aspects of the present invention will be described indetail with reference to FIGS. 1-12.

FIG. 1 is a partial sectional view showing a motor and a control boardaccording to a first embodiment of the present invention. FIG. 2 is aplan view showing a wire-installed assembly constituting the motor. FIG.3 is a sectional view showing the assembly. FIG. 4 is a plan viewshowing a terminal pin. FIG. 5 is a side view showing the terminal pin.FIG. 6 is a side view showing the terminal pin rotated by 90° from thestate shown in FIG. 5.

The outlook of the construction of the motor is described from the viewpoint of its function. A shaft 58 serving as a part of a bearing isfixed to the center of a bracket 57 which supports a rotor 64. A radialbearing is constituted by the shaft 58; a rotary cylindrical sleeve 62afitted on the shaft 58 with a certain gap therebetween; and oil (notshown) filled between the shaft 58 and the sleeve 62a. The sleeve 62a isformed integrally with the inner peripheral surface of a hub 62, thussupporting the hub 62. A collar 65 is fixed to the upper end of theshaft 58, and a thrust plate 63 disposed above the collar 65 is fixed tothe hub 62. Oil is filled in gaps positioned above and below the collar65, thus constituting a thrust bearing and functioning as a means forpreventing the rotor 64 from being removed. A herringbone groove and aspiral groove are formed on the bearing surface of the radial bearingand the bearing surface of the thrust bearing, respectively. Theconstruction of the herringbone groove and that of the spiral groove arenot described below because they are not a subject of the presentinvention.

The force for driving the motor is generated by a rotating magneticfield generated by a core 53 excited via a coil 55 wound around the core53 and a multipolar magnet 60 surrounding the core 53. The rotor 64 isconstituted by the magnet 60, a frame 61 disposed at the periphery ofthe magnet 60, and the hub 62 disposed at the periphery of the frame 61.The core 53 fixed to the bracket 57 functions as the source for drivingthe motor. In order to feed electric current from a coil 55 to a controlboard 69, a lead wire 56 of the coil 55 is connected to and wound aroundone end of a terminal pin 51, and the other end of the terminal pin 51is extended to the outside of the motor and connected with the controlboard 69.

A means for assembling the motor is described below.

A means for constituting a wire-installed assembly 50 which is one ofthe main parts of the motor according to the embodiment is describedbelow with reference to FIGS. 2-6. The assembled body shown in FIGS. 2and 3 is called the wire-installed assembly 50. As shown in FIGS. 4-6,the main portion of the terminal pin 51 is made of a metal wire circularin section, while the upper portion thereof is rectangular in section.As shown in FIGS. 2 and 3, an upper terminal holder 54a and a lowerterminal holder 52a are made of synthetic resin, especiallythermoplastic resin, and are formed on the inner peripheral surface of aspace defined by a part of an upper insulator 54, a part of a lowerinsulator 52, and a core projection 53a. First, the terminal pin 51 isinserted into the lower insulator 52. Then, the core 53 and the upperinsulator 54 are sequentially placed at predetermined positions. As aresult, a shape-change point 51a (i.e. the junction between therectangular cross-sectional portion and the circular cross-sectionalportion)of the terminal pin 51 is fixed by being sandwiched between theupper terminal holder 54a and the lower terminal holder 52a. The upperterminal holder 54a is fixed, with a rectangular-section portion 51b ofthe terminal pin 51 directed radially. Then, the assembled body is seton an automatic winding apparatus so as to wind the coil 55 around eachcore projection pole 53a and at the same time wind a lead wire 56disposed at both ends of the coil 55 around the rectangular-sectionportion 51b of the terminal pin 51. Thereafter, the lead wire 56 issoldered to the rectangular-section portion 51b, and then therectangular-section portion 51b is bent radially to make its heightlower as shown in FIG. 3. Although FIGS. 2 and 3 show the state in whichthe rectangular-section portion 51b of the terminal pin 51 has beenbent, the rectangular-section portion 51b is extended straight tofacilitate the winding operation when the rectangular-section portion51b is on the automatic winding apparatus.

A stator 59 is a general name of an assembly, disposed on the stationaryside, constituted by the bracket 57, the shaft 58, and thewire-installed assembly 50. Referring to FIG. 1, first, one end of theshaft 58 is firmly fixed in a hole formed at the center of the bracket57 by using a method such as shrinkage fitting. Then, the wire-installedassembly 50 is inserted downward into the space of the bracket 57 andfixed thereto with adhesive agent or the like. In this manner, theassembling operation is completed. At this time, the lower terminalholder 52a is penetrated into a through-hole 57a of the bracket 57 underpressure, thus preventing air from communicating between the inside andthe outside of the motor through the through-hole 57a. This constructionhas an insulation function and allows the terminal pin 51 to be placedin position.

The rotor 64 is inserted into the assembled stator 59 to assemble themotor. The rotor 64 is a general name of an assembly, disposed on therotational side, constituted by mainly the magnet 60, the frame 61, thehub 62, and the thrust plate 63. With fixing means such an adhesiveagent, the magnet 60 is fixed to the inner side of the frame 61, whilethe frame 61 is fixed to the inner side of the hub 62. Then, anappropriate amount of oil is applied to the shaft 58 on the stator sideand to the bearing surface of the sleeve 62a on the rotor side. Then,the shaft 58 is inserted into the sleeve 62a to combine them with eachother. Then, the collar 65 is fixed to the upper end of the shaft 58with a screw 66, and an O-ring 67 is installed on a predeterminedposition. Then, oil is supplied to the upper surface of the collar 65.Then, the thrust plate 63 is fixed to the hub 62 with screws 68. In thismanner, the motor assembling operation is completed.

As described above, the portion relating to the electrical connection,the portion for outwardly extending the terminal pin from the motor, andthe sealing construction have a very simple construction, respectively,and thus an automatic assembly can be facilitated. The operation forelectrically connecting the motor incorporated in the apparatus and thecontrol board 69 with each other is performed by only installing asocket contact 70 on the control board 69 and inserting the terminal pin51 into the socket contact 70. This operation is performed automaticallywith ease.

In the above description, the conductive member, namely, the terminalpin used as a relay for feeding electric current between the coil insidethe motor and the control board is circular in section but may be inother configurations than a pin. The construction comprising a member,other than the terminal pin, for feeding electric current between thecoil inside the motor and the control board can be applied in thepresent invention. In the above embodiment, the lead wire is woundaround the terminal pin and connected therewith by soldering, but otherconnection methods such as welding or pressing may be used to connectboth with each other. Members for insulating the bracket from theterminal pin and placing the terminal pin in position as well as thesealing member may have a construction separate from the terminal holderfixed to the core. Such a construction is included in the presentinvention.

A brushless motor having an alternative arrangement of the terminal pinmounting structure having an alternative arrangement of the terminal pinand terminal pin mounting structure according to the present inventionis described below with reference to FIG. 7.

The method of fixing the terminal pin as shown in FIG. 7 is differentfrom that shown in FIGS. 1 and 3. Insulation paint 71 is applied to theperipheral surface of the core 53 instead of utilizing the insulator. Aterminal holder 72 and a terminal pin 73 are installed on the core 53. Aprojection 73a is formed on the terminal pin 73 at a portion thereof onthe outer side of the motor. The projection 73a contacts the end face ofthe terminal holder 72, thus preventing the terminal pin 73 from beingmoved. The coil 75 and the lead wire 76 are wound around the core 53 andthe terminal pin 73, respectively. In this manner, the winding operationis completed.

A brushless motor having a further alternative arrangement of theterminal pin and terminal pin mounting structure having a furtheralternative arrangement the terminal pin and terminal pin mountingstructure according to the present invention is described below withreference to FIG. 8.

FIG. 8 shows another method of fixing a terminal pin. In thisarrangement, a small projection 77a formed on a terminal pin 77 isinserted into a terminal holder 78 so as to prevent the terminal pin 77from moving in the axial direction thereof. Other constructions aresimilar to those of the second embodiment shown in FIG. 7.

A brushless motor according to a fourth embodiment of the presentinvention is described below with reference to FIGS. 9 and 10.

FIGS. 9 and 10 are enlarged views showing in detail a part of thecoil-installed assembly shown in FIGS. 2 and 3. A PAC for connectedlylaminating the cores 53 one on the other is mounted on the outer side ofthe core projection pole 53a. A width (Width 2) of the core projectionpole 53a on the outer peripheral side thereof is greater than the width(Width 1) on the inner peripheral side thereof. Preferably, the width(Width 1) of the core projection pole 53a on the inner peripheral sidethereof is smaller than the width (Width 2) on the outer peripheral sidethereof by 0.1 mm or more. This configuration secures the space forperforming PAC and the winding space on the inner peripheral side of thecore projection pole 53a, and allows the coil 55 to be wound in order.

The coil 55 is wound around the core 53 in five layers. The windingpattern of the coil 55 is different from the conventional reciprocationtype in the fourth and fifth layers of the coil 55. That is, in thefourth layer, a coil 55a is wound from the outer peripheral side of thecore projection pole 53a toward the inner peripheral side thereof butjumped to the outer peripheral side thereof and then further woundtoward the inner peripheral side thereof. In this winding pattern, thetermination end of the coil 55a is positioned on the inner peripheralside of the core projection pole 53a, and a large amount of the coil 55is distributed to the outer peripheral side of the core projection pole53a. This construction does not cause the arrangement of the coil 55 tobe in disorder. This construction improves the performance of the motorby 10-20% compared with the conventional construction.

FIGS. 9 and 10 are partial sectional views showing the bracket 57 aswell as the coil-installed assembly. The thickness (Thick 2) of thebottom wall of the bracket 57 on the inner peripheral side thereof isset to be greater than the thickness (Thick 1) of the bottom wall of thebracket 57 on the outer peripheral side thereof so as to improve therigidity of the bracket 57. The distribution of a large amount of thecoil 55 to the outer peripheral side of the core projection pole 53aprovides a space in the vicinity of the inner peripheral side thereof.Preferably, the thickness (Thick 2) of the inner peripheral side of thebottom wall of the bracket 57 is greater than a thickness (Thick 1) ofan outer peripheral side of the bottom wall thereof by 0.2 mm or more.This configuration allows the winding space to be secured on the innerperipheral side of the core projection pole and the coil 55 to be woundin order while being viewed from the side of the bracket 57.

The increase of the thickness of the bottom wall of the bracket 57 fromthe outer peripheral side thereof toward the inner peripheral sidethereof may be continuous or stepped.

Details of a sleeve, bracket and members in the vicinity thereof for thebrushless motor according to the present invention are described belowwith reference to FIGS. 11 and 12. This description concerns theinvention regarding the periphery of the sleeve 62a and the bracket 57.FIG. 11 is a sectional view showing the whole of the sleeve 62a and thebracket 57. FIG. 12 is an enlarged sectional view showing the peripheryof the sleeve 62a encircled by XII in FIG. 11. In the gap between thelower end face 62b of the sleeve 62a and the upper end face 57b, of thebracket 57, opposed to the lower end face 62b, a gap (Gap 2) on theouter peripheral side of the sleeve 62a is greater than a gap (Gap 1) onthe inner peripheral side thereof. Preferably, the distance of the gap(Gap 1) between the lower end face of the sleeve 62a and the memberopposed thereto on the inner peripheral side of the sleeve 62a issmaller than the distance of the gap (Gap 2) on the outer peripheralside of the sleeve 62a by 0.03 mm or more. In this construction, surfacetension of oil causes the oil to move to the inner peripheral side ofthe sleeve 62a.

The principal object of the provision of a cylindrical portion 57c ofthe bracket 57 is to fix the core 53. In order to obtain the sameeffect, an appropriate gap is provided between the cylindrical portion57c and an outer peripheral surface 62c of the sleeve 62a. That is, agap (Gap 3) disposed at the lower end face 62b of the sleeve 62a is setto be smaller than a gap (Gap 4) disposed on the upper end face of thesleeve 62a. Preferably, the gap is substantially cylindrical between theouter peripheral surface of the sleeve 62a and the inner peripheralsurface of the stationary member and is so formed that the distance ofthe gap (Gap 3) on the lower end face of the sleeve 62a is smaller thanthe distance of the gap (Gap 4) on the upper end side thereof by 0.05 mmor more.

Further, the outer diameter (Dia 1) of the sleeve 62a at the lower endface 62b of the sleeve 62a is greater that the outer diameter (Dia 2) atthe upper end face thereof, preferably, by 0.1 mm or more. FIG. 12 showsthe effect to be obtained by this construction. That is, centrifugalforce acts on oil which has attached to the outer peripheral surface 62cof the sleeve 62a, while the oil is sucked to the outer peripheralsurface 62c by adhesion force acting in the direction perpendicular tothe vertical surface of the sleeve 62a. Because the outer peripheralsurface 62c of the sleeve 62a is inclined, the resultant vector of bothforces becomes a sliding force. Accordingly, the oil moves along theouter peripheral surface 62c of the sleeve 62a as shown in an arrow inFIG. 12. That is, the oil which has attached to the outer peripheralside 62c of the sleeve 62a moves toward the lower end face 62b thereof.

Although it is most favorable that a part of the bracket 57 confrontsthe sleeve 62a, a member separate from the bracket 57 may be provided toconfront the sleeve 62a.

An installation reference plane to install the motor is set on thebracket 57. That is, the lower surface 57d of the outer peripheralportion of the bracket 57 and the cylindrical outer peripheral portion57e have a finished surface with high accuracy. In order to prevent themotor from contacting the lower surface 57d and the cylindrical outerperipheral portion 57e to the utmost, a cylindrical peripheral portion57f having a small diameter is formed below the cylindrical outerperipheral portion 57e. That is, the diameter (Dia 4) of the cylindricalperipheral portion 57f is smaller the diameter (Dia 3) of thecylindrical peripheral portion 57e by approximately 1 mm or more. Inmounting the motor on the bracket 57, the cylindrical portion 57f iscontacted by the motor-placing platform 99. Preferably, the cylindricalperipheral portion 57f of the bracket 57 is stepped in the vicinity ofthe bottom of the bracket 57 such that the diameter (Dia 4) of thestepped portion is smaller than those (Dia 3) of other outer peripheralportions by 0.8 mm or more.

Although the description has been made by selecting examples easy tounderstand, it is to be noted that various changes and modificationswill be apparent to those skilled in the art so far as they are includedwithin the scope of the present invention.

As described above, the method, according to the present invention, ofdirectly connecting the motor and the control circuit with each other bymeans of the terminal pin provides a very simple connection constructionfor feeding electric current, a very simple electrical insulationconstruction, and a very simple sealing construction. Theseconstructions allow assembling processes to be greatly reduced and themotor and the apparatus to be miniaturized, and moreover allow the spacein the motor to be utilized efficiently. The space factor of the coilimproves the performance of the motor by 10-20% over the conventionalmotor. The increased rigidity of the motor leads to generation of a lowdegree of vibration and low noise. In addition, the oiloutflow-preventing construction of the bearing enables the motor to bedriven reliably. Moreover, the stepped portion of the bracket preventsthe bracket from being damaged, thus maintaining the accuracy andquality of the motor.

Owing to the above-described operation and effect, the motor and thedisc-driving apparatus with the motor are compact and have a highoutput, outstanding performance, and high productivity, thus comprisingthe demands.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications will be apparent to those skilled in the art. Such changesand modifications are to be understood as included within the scope ofthe present invention as defined by the appended claims unless theydepart therefrom.

What is claimed is:
 1. A brushless motor comprising:a core having acenter axis and a plurality of circumferentially spaced apart, radiallyextending projection poles; a motor energization coil wrapped about saidprojection poles; a shaft; a rotary sleeve surrounding said shaft, saidrotary sleeve having an end face at a first axial end thereof; acylindrical stationary member surrounding said sleeve, with anaxially-extendind cylindrical gap formed between said stationary memberand said sleeve; and wherein said cylindrical gap between saidstationary member and said sleeve is axially tapered so as to be smallerat said first axial end of said rotary sleeve than at a second axial endportion thereof.
 2. The brushless motor as claimed in claim 1,whereinsaid sleeve is tapered so as to have a diameter larger at saidfirst axial end than at said second axial end portion.
 3. The brushlessmotor as claimed in claim 1, whereineach of said projection poles has ara dially inner peripheral portion and a radially outer peripheralportion, and said coil is wrapped between the radially inner peripheralportion and the radially outer peripheral portion, and said radiallyinner peripheral portion has a tapered width smaller than a width, inthe circumferential direction of said core, of said radially outerperipheral portion.
 4. The brushless motor as claimed in claim 3,whereinsaid cylindrical gap is smaller by at least 0.05 mm at said firstaxial end of said rotary sleeve than at said second axial end portion ofsaid rotary sleeve.
 5. A brushless motor comprising:a core having acenter axis and a plurality of circumferentially spaced apart, radiallyextending projection poles; a motor energization coil wrapped about saidprojection poles; a shaft; a rotary sleeve surrounding said shaft, saidrotary sleeve having an end face at a first axial end thereof; whereinsaid rotary sleeve is axially conical, so as to have a diameter at saidfirst axial end which is greater than a diameter at a second axial endportion.
 6. The brushless motor as claimed in claim 5, whereinsaiddiameter at said first axial end of said rotary sleeve is greater thansaid diameter at said second axial end portion of said rotary sleeve byat least 0.1 mm.
 7. The brushless motor as claimed in claim 5,whereineach of said projection poles has a radially inner peripheralportion and a radially outer peripheral portion, and said coil iswrapped between the radially inner peripheral portion and the radiallyouter peripheral portion, and said radially inner peripheral portion hasa tapered width, in a circumferential direction of said core, smallerthan a width, in the circumferential direction of said core, of saidradially outer peripheral portion.